Telephone system



Dec. 6, 1938. R L STOKELY 2,139,247

' TELEPHONE SYSTEM 4 Filed June l1, 1935 DIFFERENT/AL RING/Na lm'.

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AT TORNEV Patented Dec. 6, 1938 PATENT QFFECE TELEPHONE SYSTEM Ray L.Stokely, Floral Park, N. Y., assigner to Bell Telephone Laboratories,Incorporated, New YorlnN. Y., a corporation of New York ApplicationJune11, 1935, Serial No. 26,027

17 Claims.

This invention relates to telephone systems and particularly to dialtelephone systems.

-The` object of the invention is theprovis'ion of improved circuitarrangements for use in automatically completing calls to and from linesof highresistance and poor insulation.

This invention is a line circuit arrangement comprising an impulserepeater for a single-wire party line in an` automatic telephone system.According to this invention, circuit means is provided for operativelyextending a subscribers line to an individual impulse repeater inresponse to the origination of a call by the removal of the receiver ata station on the line. The impulse repeater comprises a sensitiveimpulse relay and circuit Ameans responsive to the opening of theimpulsecircuit for disconnecting the winding of the impulse relay fromthe line to insure release of this relay. ,p

A feature of the invention is the provision of circuit means fordelaying the connection of the line to the associated impulse repeaterfor a predetermined short interval of time so that the callingsubscriber may ascertain whether the line is in use before callinganother station on vthe same line.

Another feature of the invention is means Vcomprising a ring-up relay,for operation when the subscriber at one station calls another stationon the line, to prevent the operative extension o f the line to theassociated. impulse repeater.

Another feature of the invention is circuit means for restoring theringup relay of a line circuit upon completion of a call between twostations on the line, thereby enabling the operative extension of theline to an associated irnpulse repeater upon the subsequent initiationof a call from this line to a station on another line.

Another feature of the invention is circuit means comprising the ring-uprelay of a magneto line for operating a' permanent .signal alarm in casethe line becomes permanently grounded due to the removal of the receiverat a station on the line or due to a trouble condition.

These and other features of the invention will be readily understood byconsidering a telephone system in which the invention is embodied. Onesuch system is illustrated schematically in the drawing which forms apart of this specification. The invention is not'limited in itsapplication to the system shown in the drawing but may, in general, beapplied to any system which includes one or more polystation lines, the`subscribers stations of which are each provided with a magnetoforsignaling other stations on the same nline Referring to the drawing,A, B and C represent local battery subscribers stations connected to apolystation single-wire line I2, D and E represent other subscribersstations in the system, L-iZ represents apparatus individual to the lineI2 in a central office, LF-I and LF-Z represent 1 line-finder switchesin the central oice, and, -SC-l and SC-Z represent selector-connectorswitches in this office.

Each of the pclystation-line subscribers stations comprises a receiver 9and transmitter 'I, a dial impulse sender I I, and a magneto Ill. Thesubscribers stations D and E are shown as being common battery stations,the station E being equipped with'a dial impulse sender for use inestablishing desired connections. The line apparatus L--IZ comprises aline relay I9, a ring-up relay 2|, a cut-through relay I5, a cut-throughdelayrelay I4, impulse relays and 26, an auxiliary impulse relay 2l, aslow-to-release relay 28, a cut-off relay 23, a release-control relayI8,

a repeating coil I6, and an interrupter mechanism which is representedby the magnet 3D and two sets of contact springs 3I and 32. For use onlywhen a station on line I2 is called from a station `on some other lineof the system, the line apparatus T r-IZ also includes an incoming-callline relay 4I, slow-to-release relays 42 and 43, a cut-off relay 24, abusy-test relay 45, a reversing relay 46, a ringing-control relay 48,and a ringing-code switch which is represented by stepping magnet 50,release magnet 53 and bank 5I.

The line-finder and selector-connector switches LF-I, LF-2, SC-I andSC-2 may be of the well-known Strowger type and reference may `be had tomy Patent No. 1,910,972, granted May 23, 1933 and to Patent No.1,941,085, granted to A. E. Hague et al. December 26, 1933 for a morecomplete description of the operation and control of theselectornconnector switches. For a description of the operation andcontrol of a Strowger type switch when used as a line-n'der, referencemay be had to my Patent No. l.,'?99,554, granted April 7, 1931. If thesystem includes a large number of lines, additional selector switchesmay be required for the establishment of desired connections and theselector-connectors SC-I and SC-2 will in that case be replaced by aconnector switch. Reference may be had to Automatic Telephony by Smithand Campbell, 2nd edition, pages53 to 65, inclusive, for a de# scriptionof the operation and control of a Strowger type switch when used as aconnector or selector.

Assume first that a call is originated at station A of the polystationline I2 and that station D is the called station. Upon removal of thereceiver from the receiver hook at station A, a circuit is closed fromground through the impulse contacts of dial II through the receiver 9and left winding of the induction coil 8, left upper contact of thereceiver hook, over line I2 to the central ofhce, through the backcontact of relay 48, normally closed contacts of ythe upper continuitysprings of relay I5, and through the winding of relay I9 to battery.Relay I9, being operated by the current in this circuit, closes acircuit for operating the slow-to-release relay 28. The operation ofrelay 28 connects ground potential to conductor 29, to prevent seizureof the line L-I2 on an incoming call by a selectorconnector SC-Z, andcloses a circuit for operating the start magnet 30 of an interrupterwhich is common to a plurality of lines. The interrupter contacts 3| and32 are each periodically .closed for a short interval, for instance .2of a second, the interval between closures being of such a length, forinstance ve seconds, that a subscriber who has removed his receiver toascertain whether or not the line is in use before operating the magnetoto call another station on the same line will have replaced the receiverbefore an idle line-finder begins hunting for the terminals belonging tothis line, as

.hereinafter described. Each closure of interrupter contacts 3| beginswhen a closure of contacts 32 ends. As soon, after relay I9 operates,Vas interruptor contacts 3| are closed, the cutthrough delay relay I4 isoperated by the current iny a circuit through its upper winding, middlelower front contact of relay I9, inner lower back contact of relay 2|and the interrupter contacts 3|. Relay I4 closes a locking circuitthrough Yits lower winding and lower front contact, upper front contactof relay I9, over conductor 29 to ground at the upper front contact ofrelay 28. W'hen interrupter contacts 32 next close, several secondsafter relay I4 operates, a circuit is closed through contacts 32, thelowermost front contact of relay I4, back contact of the lowercontinuity spring of relay I5, upper back contact of relay 2| andthrough the Winding of relay I5. Relay I5, operated by the current inthis circuit, locks through the front contact of its lower continuityspring over conductor 29 to ground at relay 28, opens the operatingcircuit for the interrupter start magnet 30, disconnects the Winding ofrelay I9 from the line I2 and closes a circuit over line I2, through thefront contact of the upper continuity spring of relay I5, upper backcontact of relay 21, winding of relay 26, and through the upper Windingof relay 25. Thus the operation of relay I5 causes the release of relaysI9 and I4 and the operation of relays 25 and 26. Relay 26 closes acircuit for holding relay 28 operated after relay I 9 releases andbridges the right winding of repeating coil I6 across conductors 33 and34. Relay 25 closes a circuit for operating relay 21 and relay 21 locksin parallel with relay 28. Since the inner lower front contacts of relay25 are in parallel with the upper back contacts of relay 21, theoperation of relay 21 does not cause the release of relays 25 and 26.With relay 21 operated, the lower winding of relay 25 is connected inparallel `with its upper Winding and ground is connected through theuppermost front contact of relay 21 and the inner lower back contact ofrelay 24 to conductor I3 to start an idle linender, which is representedby the finder LF--I, to establish connection with the line apparatusL-I2. With relay 25 operated, the winding of cut-01T relay 23 isconnected through the inner upper front contact of relay 25 and thelowermost back contact of relay 2|, over conductor 35, to the sleeveterminal of the set of terminals in the bank of each of the associatedlinenders.

When a line-nder LF-I finds and connects to the terminals to which theconductors 33, 34, 35 and 36 are connected, ground potential isconnected through the sleeve brush of the linefinder to sleeve conductor35, the cut-01T relay 23 being thereby operated in the usual manner.Relay 23 disconnects ground from conductor I3 and connects its windingto sleeve conductor 29 so as to be held operated independent of theground potential which caused its operatiorr. With relay 26 heldoperated in series with line I2,l the right winding of repeating coil I6is connected through conductors 33 and 34 and the brushes of theline-nder LF-I to the windings of the line relay (not shown) ofselectorconnector SC-L Dial tone is thereupon transmitted from theselector-connector SC-I to the calling station and nothing furtheroccurs until the subscriber at station A dials the number of the stationwith which connection is desired. The off-normal (upper) contacts of thedial II are effective to open the'transmitter circuit and short-circuitthe receiver while each series of dial impulses is being transmitted.Relay 26 is fast in operating although the line I2 be of highresistance. The energization of the lower winding of relay 25, uponoperation of relay 21, is in velectromagnetic opposition to theenergization of its upper winding, the resultant energization being onlysufcient to hold the relay operated. 'I'he release of relay 25, eachtime the line circuit is opened at the dial contacts, is therebyinsured,

although the line insulation resistance be low.

The rst opening of the line circuit by the dial is, therefore, effectiveto cause the release of relay 25; and the release of relay 25 causes therelease of relay 26, the windings of relays 25 and 26 being entirelydisconnected from the line when relay 25 releases and until relay 21releases. The release of relay 26 opens the holding circuit for relay 21and opens the bridge across conductors 33 and 34 to cause the release ofthe line relay (not shown) of selector-connector SC-I. The closing ofthe line circuit at the end of the rst dial impulse causes thereoperation of relays 25, 26 and 21 in the order named thereby againclosing the bridge across conductors 33 and 34 to cause the reoperationof the line relay of the selector-connector SC-|. Relay 28 isslow-in-releasing and remains operated during dialing. Each succeedingopening and closing of the impulse contacts of the dial causes therelease and reoperation of relays 25,

26 and 21 whereby the impulses are repeated by the uppermost contacts ofrelay 26 to control the operation of the selector-connector SC-I. Uponcompletion of the desired connection and answer of the calledsubscriber, the talking circuit includes repeating coil I6. When thesubscriber at station A replaces the receiver on the receiver-hook,relays 25, 26 and 21 release. Since relay 26 does not reoperate, relay28 releases thereby causing the release of relay I5 and A thereuponoperates the magneto I0 to call the desired station. The ringingcurrent, thus generated, is also effective to operate the ring-up relay2| in the central oice, the winding of this relay being connectedthrough condenser 23 to `line I2. Relay I9 may respond to the magnetoringing current. Relay 2| locks, through its upper front contact toground at the lowermost back contact of relay I5 and closes a circuitfor .operating relay 28 to protect the line apparatus L-I2 from seizureon an incoming call. When the receiver is again removed at station A` toconverse with the called station, relay I9 reoperates. If interruptercontacts 3| are closed When relay 2| operates, the upper winding ofrelay I8 will be energized; but as soon as relay' I9 reoperates, relayI8 will be released, With relay 2| operated, the operation of relay I9is` ineffective to cause the operation of relay I5. When theconversation is nished, relay I9 releases and as soon thereafter as theinterrupter contacts 3| are closed, the upperl winding of relay I3 isenergized and relay I8 operates. Relay |8 locks through its. lowerwinding and lower front contact, through a back contact of relay I9,over conductor 29 to ground at relay 28. When the interrupter contacts32 are next closed, a circuit is closed through the upper front contactof relay I8 for operating relay I5. The operation of relay I5 causes therelease of relay 2|; and the release of relay 2| causes the release ofrelay 28. With relays 2| and 28 released, relaysx|84 and I5 alsorelease, the line apparatus then being normal ready for use on anothercall.

If a call is originated by removing the receiver at any station of lineI2, and, after extension of the line by a line-lnder such as LF-I to aselector-connector, the calling subscriber does not dial, theselector-connector operates as described in the aforementioned PatentNo. 1,941,085 to connect ground potential to the fourth or controlconductor of line-iinder LF-I, this ground potential being extended overconductor 38 to cause the operation of relay 2|. The operation of relay2| causes the release of relay I5; and the release of relay I5 closesthe locking circuit for relay 2| and reconnects relay I9 to the line I2.The reoperation of relay I9, with relay 42|l operated, connects groundthrough the inner lower front contacts Yof these relays, to operate thepermanent signal alarm ap-paratus 22. Upon termination of the permanentsignal condition, the line apparatus L-IZ is restored to normal asdescribed in the preceding paragraph.

If a subscriber at some other station E calls a station on line I2, thecalling` line is extended by means of a line-finder LF-Z and aselectorconnector SC-2 to conductors 3l' and 38, thereby closing a loopcircuit for operating the incomingcall relay 4I. Relay 4| closes acircuit for4 operating relay 42 and relay 42 connects a busy-indieatingground potential to sleeve conductor 29 to prevent seizure of the lineon another call, to` hold-the selector connector SC--2, and to cause theoperation of the auxiliary cut-olf relay 24. Relay 24 locks through itsinner upper front contact directly to conductor 29, closes a circuit foroperating relay I5, and connects the right winding of repeating coil I6,through con- 5 densers 60, to conductors 3l and 38. Relay I5 disconnectsline I 2 from relays I9 and 2| and connects line I2 to relays 25 and 26,which relays are thereupon operated. Since the auxiliary cut-01T relay22 is then operated, the oper- =l0 ation of relay 2'I is ineffective tocause the starting of a line-nder.

Since the line apparatus L-I2 is arranged to control the ringing of thevarious stations on line I2, the selector-connector SC--Z differs fromthat described in the above-mentioned Patent No. 1,941,085 in that itlacks the ringing-control apparatus. The dial impulses created bythedialing of the ringing-code digit are repeated by the selector-connectorSC-2 to cause the alternate release and reoperation of relay 4I. Thefirst release of relay 4| closes a circuit for operating relay 43 androtary stepping magnet 5U; and the reoperation of relay 4|, at the endof the rst impulse, causes the release of magnet .25 58. The operationof magnet 50 advances the brush 5| of the ringing-code selector onestep. The off-normal contacts ON are shifted when the selector is movedout of normal position, the circuit for relay 43 and magnet 59 beingthereupon changed to include the lower front contact of relay 43 insteadof the lower contacts of the ON springs. Each succeeding release andreoperation of relay il causes a corresponding operation and release ofmagnet 5I), the brush 5I being advanced one step by each operation ofmagnet 5B. Relay43 is slow-in-releasing and remains operated until allof the ringing-codedigit impulses have been received. Relay l42 is alsoslow-in-releasing and does not release during the responseof relay I tothe dial impulses. The aforementioned operation of relay 43 also closesa circuit for operating relay 45; this circuit includes the uppermostfront contact of relay t3, the lower back contact of relay 2'I,conductor 23 and the upper front contact of relay 42. Relay 45 locksthrough its upper front Contact and opens the connection between therepeating coil Iii and conductor 38. The brush of ringing-controlinterrupter drum 55 is connected to ground during the ringing intervalof all the different ringing codes; and, if relay 43 is operated duringthe time this brush is connected to ground, relay i5 operates. If relay43 releases before ground is disconnected from the 55 brush of drum 55,relay I4 is held operated through its upper front contact, the lowerfront contact of relay 45 and the back contact of relay 43. Relay I4 andinterrupter drum` 55 are thus effective, in combination with relays 43and 45, to prevent the operation of relay 48 at any time other than atthe beginning oi a ringing cycle. With relay It reieased, relay 48 isoperated at the beginning of the next ringing cycle to disconnect lineI2 from the windings of relays 25 ,65 and and connect line I2 throughbrush 5I and the terminal lwith which it is in contact, through theringing interrupter 5? tothe ringing source: 53. The `particular ringingcode selected by brush 5i is thereby transmitted over line I2, 70 theringer-s at all of the stations on the line being operated. The brush 5iof the code selector is. shown as having ten terminals; if more than tenstations are connected to line I2, a `code selector with a larger numberof terminals would g5 -be provided, in which case the ringing code would.consist .of more than one digit. A ringing tone is transmitted throughcondenser 49 to the calling station E. The release of relay 48 .at theend -of the ringing interval reconnects 'line I2 to relays 25 .and 26.Since the high resistance, high .capacity .and low insulation resistanceof single- --wire lines are such as to make it impossible to use -aringing cut-off relay in series with the line, it is necessary toreconnect the line to the sensitive impulse relays 25 and 26 at the endof each ringing cycle for operation if the receiver has vbeen removed atthe called station. Relay 48 1s slow-in-releasing so as to permitdischarge of 'the ringing condenser at the various stations before theline I2 is reconnected to relays 25 and 2.6, to guard against falseoperation of these relays. When the receiver is removed from thereceiver-hook at the called ystation and as soon thereafter as relay 48releases, yrelays 25, 26 and 21 are operated. The operation of relay 21causes the release of relay 45` thereby preventing `the reoperation ofrelay 48 when the brush of interrupter drum 55 is next connected toground. The release of relay 45 also completes the talking circuitthrough the right winding of repeating coil I6. The operation `of relay25 closes a circuit for operating the reversing relay 45. The operationof relay 28 causes the operation of relay 28. When the connection isreleased by the calling subscriber, relays 4I, 42 and 46 release.` Therelease of relay 42 causes the operation of releasemagnet 53 therebyrestoring the ringing-code selector to normal. When the receiver isreplaced at the called station, relays 25, 26, 21 and 28 release. Therelease of relay 25 causes the release of relay 46, if operated. Withboth of relays 42 and 28 released, ground is vdisconnected from sleeveconductor `25! thereby causing the release of relays 24 and I5.

What is claimed is:

ll. In a telephone system, a line, a subscribers station, an impulsesender at said station, an impulse repeater for said line and no other,and circuit means responsive to the removal of the receiver from thereceiver-hook at said station for operatively extending said line tosaid impulse repeater.

2. In a `telephone system., a single-Wire line, -a subscribers station,an impulse sender at said station, an impulse repeater for said line andno other, and circuit means responsive to the removal of the receiverfrom `the receiver-hook at said station for operatively extending saidline to said impulse repeater.

3. In a telephone system, a line, a subscribers station, an impulsesender at said station, an `impulse repeater individual to said line,circuit means effective a predetermined interval of time aftr theremoval of the receiver from the receiver-hook at said station foroperatively extending said line to said impulse repeater.

4'. In a telephone system, a line, a subscribers station,` an impulsesender at said station, an impulse repeater individual to said line, aline relay for responding to the removal of the receiver from thereceiver-hook at said station, a switching relay for operativelyextending said line to said impulse repeater, and circuit meanseffective a predetermined interval of time after the oper- 4ation, ofsaid line relay for operating said switching relay.

5. In a telephone system, a line, a subscribers station, an impulsesender at said station, an ,impulse repeater individual to said line, .aline vrelay for responding :to the removal lof the receiver from thereceiver-hook at said station, a

yswitching relay for transferring said line from said line relay to saidimpulse repeater, and circuit means eifective a predetermined intervalof time after the operation of said line relay for operating saidswitching relay.

6. In a signaling system, a line, an impulse sender, an impulse relay,an auxiliary impulse relay, -a signaling circuit comprising said `lineand .sender and windings of said impulse relays 1n series, said impulserelay being `adjusted to operate in series with a line of lowconductivity and said auxiliary impulse relay being adjusted to releasein series with a line of low insulation resistance, a third relay, acircuit closed by :the operation of said second relay for operating saidthird relay, a circuit for holding said third relay operated until said`impulse relay releases, a second winding of said auxiliary relaydifferentially energized with respect to its rst winding upon operationof said third relay, and means com.- prising normally open contacts ofsaid second relay for disconnecting said line from the winding of saidimpulse relay.

7. In a telephone system, a line, subscribers "stations connected tosaid line, means at each station for transmitting ringing current overthe line to signal another of the stations, an impulse repeater for saidline, circuit means responsive to the removal of the receiver at any oneof said stations for operatively extending said line to said impulserepeater, and means comprising a relay operatively responsive to ringingcurrent over said line for preventing said extension of the line to theimpulse repeater.

8. In a telephone system according to claim 7, means responsive to thereplacing of the receivers at the calling and called stations on a callbetween two stations on said line for causing the release of said relayto render said circuit means operative for use on a succeeding calloriginating at one of said stations.

.9. In a telephone system, a line, subscribers .stations connected tosaid line, a magneto at each station for transmitting ringing currentover the line to signal any other station on the line, a relay forresponding to ringing current over said line, .an automatic switch foruse in completing a call originating over said line, circuit .meansresponsive to the removal of the receiver `at any of said stations foroperatively extending rsaid line to said switch, alarm signal means, andcircuit means including said relay for disconnecting said line from saidswitch and for operating said alarm signal means.

l0. In a signaling system, a line, an impulse sender, an impulse relay,a second relay, a signaling circuit comprising said line and sender anda winding of each of said relays, said impulse relay being adjusted weakand said auxiliary relay being adjusted stiff, a third relay, andcircuit means comprising said second and third relays effective inresponse to the opening of said signaling circuit for disconnecting thewinding of said impulse relay from the line.

l1. In a signaling system, a line, an impulse sender, an impulse relay,a signaling circuit comprising said line and sender and the winding ofsaid relay, and circuit means comprising another relay operativelyresponsive to the opening of said circuit Afor disconnecting the windingof said impulse relay from said line.

12. In a telephone system, a line, a subscribers station connected tosaid line, an impulse repeater permanently connected to said line,circuit means responsive to the removal of the receiver from thereceiver-hook at said station for operatively associating said line andimpulse repeater, and a ydial at said station for creating signalimpulses transmitted over said line to said impulse repeater.

13. In a telephone system, lines, a plurality of subscribers stationsconnected to one of said lines, a magneto at each station for use insignaling the other stations on the line, an impulse repeater for use inestablishing a connection between any one of said stations and any otherof said lines, a relay connected to said line and operatively responsiveto signaling current from any one of said magnetos for preventing theextension of said line to said impulse repeater, and circuit means fordisconnecting said relay and for operatively extending said line to theimpulse repeater.

14. In a telephone system, a line, subscribers stations connected tosaid line, each station comprising a magneto and an impulse sender, animpulse repeater individual to said line, circuit means responsive tothe removal of the receiver at any one of the stations for operativelyextending said line to the impulse repeater, and a relay operativelyresponsive to ringing current created by the operation of the magneto atany of said stations for preventing the extension of said line to saidimpulse repeater.

15. In a telephone system, a line, subscribers stations connected tosaid line, each station comprising a magneto and an impulse sen-der, animpulse repeater individual to said line, circuit means responsive tothe removal of the receiver at any of said stations to originate a callfor operatively extending said line to the impulse repeater, a relayoperatively responsive to ringing current created by the operation ofthe magneto at any of said stations for preventing the extension of saidline to said impulse repeater, and circuit means rendered effective bythe return of the receiver to normal position for causing the release ofsaid relay to enable extension of said line to said repeater on asubsequent call.

16. In a telephone system, lines, one of said lines being a party line,a magneto at each of the stations of said party line for use in callingthe stations on the line, an impulse sender at each of said stations foruse in calling stations connected to other lines, an impulse repeaterfor use in completing calls from any one of said party line stationstostations connected to other lines, a line relay responsive to theremoval of the receiver at any one of said party line stations, aring-up relay responsive to current created by the operation of themagneto at any of said party line stations, circuit means effective apredetermined interval of time after the operation of said line relayfor disconnecting said ring-up relay from the line and for operativelyconnecting said line to said impulse repeater, circuit means renderedeiective by the operation of said ring-up relay for preventing theextension of said line to said impulse repeater, circuit means forholding said ring-up relay operated during conversation between stationsof said party line, and circuit means effective a predetermined intervalof time after the return of the receivers to normal at the calling andcalled stations of said party line for causing the release of saidring-up relay.

17. In a telephone system, lines including a line having a plurality ofmagneto stations permanently connected thereto, an impulse sender ateach of said stations, means comprising impulse controlled switches foruse in connecting said line to a desired one of the other lines, animpulse repeating relay for repeating impulses from said sender toI saidswitches, said impulse relay being individual to but normallydisconnected from said line, and means comprising a line relay normallyconnected to said line and responsive to removal of the receiver at anyof said stations for connecting said line to said impulse repeatingrelay.

RAY L. STOKELY.

